An artificial substitute for the diaphysis (shaft) of a humerus, femur, or tibia intended to be implanted for the long-term stabilization of segmental bone defects (e.g., due to osteomyelitis, trauma, bone tumours, or non-healed fractures after osteosynthesis/revision arthroplasty). It is a modular device that typically includes a resection element (spacer), intramedullary nails (inserted into the intramedullary canal), screws, and connectors all made of metal [e.g., titanium (Ti)]; components are both sterile and non-sterile. Instruments for implantation are typically included and implantation may be performed with or without bone cement.